Biguanide derivatives as corrosion



United States BIGUANIDE DERIVATIVES AS CORROSION ITORS Joseph A. Chenicek, Bensenville, and Ralph B. Thompson,

Hinsdale, Ill., assignors to Universal Oil Products Company, Chicago, 111., a corporation of Delaware No Drawing. Application February 1, 1952, Serial No. 269,614

11 Claims. (Cl. 44-72) to water corrosion prevention 'ice , observed as a separate phase within the lubricating system larly hydrocarbons and similar organic liquid composi- 1 tions, it is often necessary to transport and/or store such materials in metal containers, as in steel or other metal pipe lines, drums, tanks, and the like. Since these materials often contain varying amounts of water in solution or in suspension which may separate, due to temperature changes, internal corrosion of the container by separating water almost invariably occurs to a greater or lesser degree. This problem is especially serious when gasoline or fuel oils are under consideration. In spite of all reasonable and practical precautions during the manufacture of gasoline or fuel oils, when the same are transported in pipe lines or stored in drums or tanks for a period of time, an appreciable quantity of water separation is found as a film or in minute droplets in the pipe line or on container walls or even in small pools in the bottom of the container. This brings about ideal conditions for corrosion and consequent damage to the metal surfaces of the container as well as the even more serious contamination of the gasoline or fuel oil or other material contained therein by the corrosion products.

As a result of the above described corrosion, it has become necessary for manufacturers and shippers of such products to apply various internal coatings to the container walls or to add corrosion inhibitors of one type or another to the product being stored or shipped. It has long been recognized, however, that one of the great difficulties in inhibiting this type of corrosion lies in the fact that those inhibitors which are soluble in organic materials are relatively ineffective in preventing water corrosion of metal surfaces. On the other hand, those inhibitors which are advantageous in preventing this type of corrosion are but slightly, if at all soluble in organic materials and their application is rendered quite difficult for these purposes.

For example, various water soluble corrosion inhibitors may be utilized for preventing corrosion of gasoline or fuel oil storage tanks by water collecting in the bottom of the tank, a suitable and sutficient quantity of the desired inhibitor being injected in the bottom of the tank -to inhibit both water already separated or intentionally maintained therein, and water which may later separate from the gasoline or fuel oil and collect in the bottom of the tank. However, part of the water which separates collects on the tank wall, corroding and damaging the same, the corrosion products in turn contaminating the gasoline or fuel oil.

Analogous corrosion problems occur in numerous other fields; for example, in the lubrication of internal combustion engines or steam engines including turbines, and other similar machinery, quantities of water are often as a result of the condensation of water from the atmosphere, or in the case of internal combustion engines as a result of dispersion or absorption in lubricating oil or water formed as a product of fuel compositions. Water, in such instances, corrodes the various metal parts of the machinery with which it comes in contact, the corrosion products causing further mechanical damages to bearing surfaces and the like due to their abrasive nature and catalytically promoting the chemical degradation of the lubricant. In this instance, as in the example cited above, the inhibitors known to the art have not always been entirely satisfactory, the organic material soluble inhibitors being, in general, relatively inefiective water corrosion inhibitors, and the water soluble inhibitors being difficult and in most instances impractical in their application. The same or similar problems arise in the preparation and use of various coating compositions such as greases, glass, household oils, paints, lacquers, Water soluble paints, etc., which are often applied to metal surfaces for protective or other purposes.

It is an object of this invention to provide potent corrosion inhibitors which are soluble in organic materials. A further object is to provide inhibitors of this type which will satisfactorily prevent corrosion of certain metal surfaces by water in contact with said organic materials and said'metal surfaces. Further objects are to provide water corrosion inhibitors which are stable at ordinary temperatures of use, easily and inexpensively prepared and which will not deleteriously affect organic materials with which they are incorporated. Other objects, together with some of the advantages to be derived when utilizing the inhibitors of the present invention, will become apparent from the following detailed description thereof.

In one embodiment the present invention relates to a non-corrosive composition of matter comprising an organic material coming in contact with water during the useful life thereof, said organic material containing dissolved therein in minor proportion, but in amount sufiicient to inhibit corrosion of metal surfaces by said water, of a biguanide derivative.

In a more specific embodiment the present invention relates to a non-corrosive composition of matter comprising an organic material coming in contact with water during the useful life thereof, said organic material having dissolved therein in minor proportion, but in amount suificient to inhibit corrosion of metal surfaces by said water, N-substituted biguanide.

In another specific embodiment the present invention relates to a non-corrosive composition of matter comprising an organic material coming in contact with water during the useful life thereof, said organic material having dissolved therein in minor proportion, but in amount suflicient to inhibit corrosion of metal surfaces by said water, a N ,N -di-substituted biguanide.

In a more specific embodiment the present invention relates to a non-corrosive composition of matter comprising an organic material coming in contact with water during the useful life thereof, said organic material having dissolved therein in minor proportion, but in amount suificient to inhibit corrosion of metal surfaces by said water, N -dodecylbiguam'de.

In still another more specific embodiment the present invention relates to a non-corrosive composition of matter comprising an organic material coming in contact with water during the useful life thereof, said organic material having dissolved therein in minor proportion, but in amount sufficient to inhibit corrosion of metal surfaces by said water, N -phenyl-N -heptylbiguanide.

in another specific embodiment the present invention relates to a non-corrosive composition of matter comprising an organic material coming in contact with water during the useful life thereof, said organic material having dissolved therein in minor proportion, but in an amount sufficient to inhibit corrosion of metal surfaces by said water, a 2,6-diamino-1,4-dihydro-l,3,5-triazine.

In another still more specific embodiment the present invention relates to a non-corrosive composition of matter comprising an organic material coming in contact with water during the useful life thereof, said organic material having dissolved therein in minor proportion, but in amount sufficient to inhibit corrosion of metal surfaces by said water, 2-amino-6-dodccylphenylamino-1,4-dihydro- 1,3,5-triazine.

It has been found, according to the present invention, that certain biguanide derivatives are excellent water corrosion inhibitors and are soluble in organic materials, thereby preventing corrosion of metal surfaces in contact with said organic material andwater. It has been found further that these biguanide derivatives, although probably soluble only in the organic material, prevent corrosion of the metal surfaces in contact with the water only, said water being in contact with said organic material.

Certain substituted biguanides for use in accordance with the present invention will have the following general structure:

where R is selected from the groups consisting of hydrocarbon and substituted hydrocarbon groups, and where R1, R2, and R3 are selected from the group consisting of hydrogen, hydrocarbon and substituted hydrocarbon groups.

In accordance with the established nomenclature the substituted biguanides are numbered as follows: Beginning with one of the terminal nitrogen atoms, in our case conveniently being the nitrogen atom at the left of the general structure, and numbering this nitrogen as 1, the remaining nitrogen atoms are numbered, reading from left to right, 2, 3, 4, and 5. Thus certain biguanide derivatives of the present invention require that one terminal nitrogen atom, number 1, be substituted by at least 1 hydrocarbon or substituted hydrocarbon group. As indicated in the general structure above, further substitution of the terminal nitrogen atoms may take place and this substitution may be such that both terminal nitrogen atoms, numbers 1 and 5, are each substituted by at least 1 hydrocarbon or substituted hydrocarbon group and may be completely substituted by hydrocarbon or substituted hydrocarbon groups.

This particular substitution is an essential feature of the present invention because it results, not only in a corrosion inhibitor which etfectively retards corrosion of metal surfaces in contact with an organic material and water, but also in a compound which is readily soluble in said organic material, and therefore, may be readily incorporated therein. As will be demonstrated further, in the examples, the readily solubility of the corrosion inhibitor in the organic material serves the function of providing a corrosion inhibitor which is effective in preventing corrosion of metal surfaces in contact both wit-h an organic material and with water in contact with said organic material.

Any suitable substituted biguanide may be used in accordance with the present invention. It generally is preferred that the additive compound contains at least 6 carbon atoms, although in some cases additives containing a fewer number of carbon atoms may be. used. N -substituted biguan'idcs containing 6. or more carbon atoms include N -hexylbiguanide, N -heptylbiguanide,

N -octylbiguanide, N -nonylbiguanide, N -decylbiguanide,

N undecylbiguanide, N dodecylbiguanide, N tri-' decylbiguanide, N tetradecylbiguanide, N pentadecylbiguanide, N hexadecylbiguanide, N heptadecylbiguanide, N octadecylbiguanide, N nonadecylbiguanide, etc., N -phenylbiguanide, N -tolylbiguanide, N -xylylbiguanide, N -naphthylbiguanide, N -ethylphenylbiguanide, N -propylphenylbiguanide, N -butylphenylbiguanide, N amylphenylbiguanide, N hexylphenylbiguanide, N -heptylphenylbiguanide, N -octylphenylbiguanide, N nonylphenylbiguanide, N decylphenylbiguanide, N -undecylphenylbiguanide, N -dodecy1- phenylbiguanide, N -tridecylphenylbiguanide, N -tetradecylphenylbiguanide, etc. Similar compounds in which the phenyl group is replaced by a naphthyl group, a substituted naphthyl group, a cyclohexyl group or a substituted cyclohcxyl group are similarly within the scope of the present invention.

Any suitable 1,5-substituted biguanide may be usedin accordance with the present invention. 1,5-substituted biguanides containing 6 or more carbon atoms include N -methyl-N -amylbiguanide, N -rnethyl-N -hexylbiguanide, N methyl-N -heptylbiguanide, N -methyl-N -octylbiguanide, N -methyl-N -nonylbiguanide, N -methyl-N decylbiguanide, N methyl N5 undecylbiguanide, N methyl-N -dodecylbiguanidc, N -methyl-N -tridecylbiguanide, N -methyl-N -tetradecylbiguanide, N -methyl-N pentadecylbiguanide, N -methyl-N -hexadecylbiguanide, N -methyl-N -heptadecylbiguanide, N -methyl-N octadecylbiguanide, N -methyl-N -nonadecylbiguanide, etc., N ethyl-N -butylbiguanide, N -ethyl-N -amylbiguanide, N -ethyl-N -hexylbiguanide, N -ethyl-N -heptylbiguanide, N -ethyl-N -octylbiguanide, N -ethyl-N -nonylbiguanide, N -ethyl-N -decylbiguanide, N -ethyl-N -undecylbiguanide, N -ethyl-N -dodecylbiguanide, N ethyl-N -tridecylbiguanide, N -ethyl-N -tetradecylbiguanide, N -ethyl-N pentadecylbiguanide, N ethyl N hexadecylbiguanide, etc., N -propyl-N -propylbiguanide, N -propyl-N -butylbiguanide, N -propyl-N -amylbiguanide, N -propyl-N hexylbiguanide, N -propyl-N -heptylbiguanide, N -propy1- N octylbiguanide, N propyl N nonylbiguanide, N propyl N decylbiguanide, N -propyl-N -undecylbiguanide, N -propyl-N -dodecylbiguanide, N -propyl-N -tridecylbiguanide, N -propyl-N -tetradecylbiguanide, N propyl-N -pentadecylbiguanide, etc., N -butyl-N -butylbiguanide, N -butyl-N -amylbiguanide, N -butyl-N -hexylbiguanide, N butyl N heptylbiguanide, N -butyl-N octylbiguanide, N -butyl-N -nonylbiguanide, N -butyl-N decylbiguanide, N -butyl-N -undecylbiguanide, N butyl N dodecylbiguanide, N -butyl-N -tridecylbiguanide, N -butyl-N -tetradecylbiguanide, N -butyl-N -pentadecylbiguanide, etc., N -amyl-N -amylbiguanide, N amyl-N -hexylbiguanide, N -amyl-N -heptylbiguanide, N amyl-N -octylbiguanide, N -amyl-N -nonylbiguanide, N amyl-N -decylbiguanide, N -amyl-N -undecylbiguanide, N -amyl-N -dodecylbiguanide, N -amylN -tridecylbiguanide, N -amyl-N -tetradecylbiguanide, N -amyl-N -pentadecylbiguanide, etc., and other N -alkyl-N -alkylbiguanides in which the total number of carbon atoms in the alkyl group is at least 6. The N -phenyl-N -a1kylbiguanides, N -t0lylN -alkylbiguanides, N -xylyl-N -alkylbiguam'dcs, N -naphthyl-N -alkylbiguanides, N -alkylphenyl- N -alkylbiguanides in which the first alkyl group may contain 2 or more carbon atoms, N -phenylalkyl- N -alkylbiguanides, and similar compounds in which the phenyl group is replaced by a naphthyl group, a substituted naphthyl group, cyclohexyl group, substituted cyclohexyl group, etc. are similarly within. the scope of the present invention. Other biguanides include N ,N -diphenylbiguanide, N -alkylphenyl- N -phenylbiguanide, N -alkylphenyl-N -alkylphenylbiguanides, N -phenylalkyl-N -phenylbiguanides, N -phenyl- 'nide, N ,N ,N ,N -tetracyclohexylalkylbiguanide, etc.

arsisov alkyl N alkylphenylbiguanides, N phenylalkyl N phenylalkylbiguanides, N -cyclohexyl-N -cyclohexylbiguanides, N -cyclohexyl-N -phenylbiguanides, N -cyclohexyl- N -phenylalkylbiguanides, N -cyclohexyl-N -alkylphenylbiguanides, N -alkylcyclohexyl-N -alkylcyclohexylbiguanides, N -alkylcyclohexyl-N -phenylbiguanides, N -cyclohexyl-N -phenylalkylbiguanides, N -alkylcyc1ohexy1-N alkylphenylbiguanides, N -cyclohexylalkyl-N -phenylbiguanides, N cyclohexylalkyl-N -phenylalkylbiguanides, N -cyclohexylalkyl-N -alkylphenylbiguanides, N -cyclo hexyl-N -alkylcyclohexylbiguanides, N -cyclohexyl-N cyclohexylalkylbiguanides, N -alkylcyclohexyl-N -alkylcyclohexylbiguanides, N -cyclohexylalkyl-N -alkylcyclohexylbiguanides, N -cyclohexylalkyl-N -cyclohexylalkylbiguanides, etc.

Trialkylbiguanides include those in which the N nitrogen atom is di-substituted and the N nitrogen atom is mono-substituted with hydrocarbon groups as hereinbe fore set forth. Typical compounds in this class include N ,N ,N triethylbiguanide, N propyl-N ,N -diethylbiguanide, N -butyl-N ,N -diethylbiguanide, etc., N -methyl- N ,N -dipropylbiguanide, N -ethyl-N ,N -d1propylb guanide, N N ,N -tripropylbiguanide, N -butyl-N ,N -d1propylbiguanide, etc., N -n1ethyl-N ,N -dibutylbiguanide, N ethyl-N ,N -dibutylbiguanide, N ,N ,N -tr1butylb1guamde, N -amyl-N ,N -dibutylbiguanide, N -hexyl-N ,N :d1butylbiguanide, etc., N -phenylN ,N -dimethylbiguamde, N ph'enyl-N ,N -diethylbiguanide, etc., N -phenyl-N -methyl- N -ethylbiguanide, N -phenyl-N -methylN -propylb1guanide, etc., N -phenyl-N ,N -dipropylbiguanide, N -phenyl- N -propyl-N -butylbiguanide, N -phenyl-N ,N -dibutylbiguanide, N -phenyl-N ,N -diamylbiguanide, N -phenyl- N ,N -dihexylbiguanide, etc., N -tolyl-N ,N -dimethy1b1- guanide, N -tolyl-N -methyl-N -ethylbiguanide, N -tolyl- N ,N -diethy1biguanide, N -tolyl-N -ethyl-N -propylb1guanide, N tolyl N ,N dipropylbiguanide, N -tolyl-N propyl N butylbiguanide, N -tolyl-N ,N -dibutylbiguanide, 'etc., N -xylyl-N ,N -dialkylbiguanides, N -alkylphenyl-N ,N -dialkylbiguanides, N -phenylalkyl-N ,N dialkylbiguanides, N -cyclohexylalkyl-N ,N -dialkylb1guanides, N -cyclohexyl-N ,N -dialkylbiguanides, N -pheny1- N -phenyl-N -alkylbiguanides, N ,N ,N -triphenylbiguanides, N -pheny1-N -phenyl-N -alkylphenylbiguanides, N phenyl-N -phenyl-N -phenylalkylbiguanides, N -phenyl- N ,N phenylalkylbiguanides, N phenyl-N ,N alkylphenylbiguanides, N alkylphenyl N phenyl-N -alkylphenylbiguanides, N phenylalkyl N -phenyl-N alkylphenylbiguanides, N ,N ,N triphenylalkylbiguanldes, N ,N ,N -trialkylphenylbiguanides, etc.

N ,N ,N ,N -tetra-substituted-biguanides are within the scope of the present invention and the substituent groups may comprise alkyl, phenyl-phenylalkyl, alkylphenyl, cyclohexyl, alkylcyclohexyl, and cyclohexylalkyl groups. Particularly preferred compounds include those in which the substituent group is the same because this simplifies manufacture of the compounds and thus include N ,N N ,N -tetraethylbiguanide, N ,N ,N ,N -tetrapropylbiguanide, N ,N ,N ,N -tetrabutylbiguanide, N ,N ,N ,N -tetraamylbiguanide, N ,N ,N ,N -tetrahexylbiguanide, N ,N N ,N -tetraheptylbiguanide, etc., N ,N ,N ,N -tetraphenylbiguanide, N ,N ,N ,N -tetraalkylphenylbiguanide, N ,N N ,N -tetraphenylalkylbiguanide, N ,N ,N ,N tetracyclohexylbiguanide, N ,N ,N ,Nitetraalkylcyclohexylbiguais to be understood, however, that these substituent groups may be different as, for example, such compounds as N ,N -diphenylbiguanide, N ,N -dibutylbiguanide, N ,N ditolylbiguanide, N ,N -diamylbiguanide, N ,N ,N -triphenyl-N -butylbiguanide, etc.

These biguanide derivatives may be prepared in any suitable manner. For example, N -phenyl-N -heptylbiguanide may be prepared by commingling the desired aryl-diazonium halide with dicyandiamide and decompoing the resultant product to aryl-dicyandiamide, which is reacted with primary heptyl amine in the presence of copper sulfate. When a tri-substituted biguanide is desired, a secondary amine is employed. The tetrasubstituted biguanides may be prepared by the reaction of two molecular proportions of the desired amine hydrochloride with sodium dicyanamide.

Other biguanide derivatives which are within the scope of the present invention are the 2,6-diamino-1,4-dihydro- 1,3,5-triazines which may be illustrated by the following general formula:

where again, R may be selected from hydrocarbon and substituted hydrocarbon groups, R1, R2 and R3 may be selected from the hydrogen, hydrocarbon and substituted hydrocarbon groups, and R4 may be selected from hydrogen, hydrocarbon and substituted hydrocarbon groups. Compounds of this structure include 2-arnino-6-dodecylphenylamino-l,4-dihydro-1,3,5-triazine, 2-amino-4-phenyl- 6 dodecylphenylamino 1,4 dihydro 1,3,5 triazine, 2- amino 4 n propyl-6-dodecylphenylamino-1,4-dihydro- 1,3,5-triazine, Z-amino-4-isopropyl-6-dodecylphenylamino- 1,4 dihydro 1,3,5 triazine, 2-amino-4-butyl-6-dodecylphenylamino-1,4-dihydro-1,3,5-triazine, 2-amino-4-amyl- 6-nonylphenylamino-1,4-dihydro-1,3,5-triazine, 2-amino- 4 hexyl 6-hexylphenylamino-1,4-dihydro-1,3,5-triazine, etc.

1,4-dihydro-1,3,5-triazines may be prepared by the reaction of biguanides with aldehydes. When substituted dihydro-1,3,5-triazines are desired, the biguanide is suitably substituted. Thus in the preparation of the preferred 2-arnino-4-n-propyl-6-dodecylphenylamino 1,4 dihydro- 1,3,5-triazine, dodecylphenylbiguanide is reacted with butyraldehyde, the reaction being efiected by merely boiling equimolecular quantities of the components or solutions thereof, with constant water separation.

It is to be understood that the corrosion inhibitors of the present invention may comprise the specific compounds named above alone or in admixture with various isomers thereof. Furthermore, it is understood that the various corrosion inhibitors which may be utilized in accordance with the present invention are not necessarily equivalent for use in the inhibition of difierent organic compounds which may be treated in accordance with the present invention. Furthermore, it is understood that the particular additive to be used should be selected so as to meet the specific requirements of the particular material being stabilized. For example, in the treatment of fuel oil, the R group should be selected so that the additive contains a total of from about 6 to about 30 carbon atoms permole in order that the additive may not be too volatile, will be readily soluble, etc. It is appreciated that the particular selection of the substituent groups will depend upon the particular organic material in which the additive is to be employed.

The presently described inhibitors are most effective in preventing water corrosion of ferrous metals, aluminum, nickel, chromium, and alloys of these metals. To a lesser extent, the biguanide derivative inhibitors are also beneficial in preventing Water corrosion of copper and copper alloys.

The inhibitors of the present invention may be incorporated into any organic material, whether solid, semisolid or liquid in which they are soluble and with which Thus they may be added to hydrocarbons (which may be paraffinic, olefinic, naphthenic, or aromatic) of the type described, or to chlorinated hydrocarbons, alcohols, esters, ethers, ketones, nitriles, amino compounds, amides, fats and fatty oils (edible and non-edible) paints, varnishes, natural waxes, oils, etc.

When adding the inhibitors to hydrocarbon oils such as gasoline, benzene, kerosene, fuel oils, cycle stocks, etc., 0.0001 to 0.5% by weight of the biguanide derivative will generally be found satisfactory for inhibition of water corrosion, although lower or higher amounts may be used. The precise amount of inhibitor to be utilized in each instance will, of course, vary with the particular conditions at hand and should be determined experimentally, particularly when usually severe corrosion conditions are to be overcome. However, in the majority of practical applications when handling substantially water insoluble organic materials of this type, the addition of approximately 0.001 to about 0.1% by weight of the inhibitor will be found satisfactory.

Larger amounts of inhibitor up to about 2.0% by weight may be required for inhibiting other organic materials, particularly those miscible with water, such as alcohols, ketones and the like, as for example, methyl alcohol, ethyl alcohol, propyl alcohol, acetone, methyl ethyl ketones, methyl vinyl ketone, dioxane, etc.

Among other suitable applications for the present inthey do not react.

vention, the following come into consideration. For

slushing oils and other rust preventive coatings, the biguanide derivatives will be found effective as corrosion inhibitors for most practical applications, when incorporated into the coatings in amounts ranging approximately as follows: Oil base coatings, 0.01% to 1% by weight; wax base coatings, other petroleum wax (petrolatum) base coatings, 0.001% to 1% by weight; petroleum wax base coatings, 0.01% to 5% by weight or higher based on the petroleum wax contained in the particular coating; a primer coating for paint, 0.01% to 1.0% by weight based on the dry constituents; lubricant compositions such as lubricating oils for internal combustion engines, turbines and the like, greases, semi-greases, etc., 0.001% to about 1.0% by weight; general purpose oils, such as household oils, 0.01% to 1.0%.

The following specific examples serve to illustrate the effectiveness of the presently disclosed corrosion inhibitors. The procedure used in each of the following examples is given as follows: The samples were stored in clear 4 ounce bottles in a 100 F. constant temperature room in the absence of light. To make up a sample, 50 grams of an oil was placed in the bottle, together with 5 ml. of distilled water or synthetic sea water. By weight, 0.01% of the corrosion inhibitor was added to the oil; the corrosion inhibitor had previously been dissolved in benzene or isopropyl alcohol in a ratio of 0.0050 grams per milliliter of solvent, and thereby the oil could accurately be inhibited by using 1 ml. of the solvent solution from a pipette. An iron strip was then added, the bottle corked and thoroughly shaken. Before storing the cork was loosened in order to allow air to enter. The iron strips were cut from mild carbon steel; the bluing was removed by dilute acid pickling with constant movement. They were then rinsed in water several times, immersed in acetone, and air dried in a low temperature oven (about 100 C.). A light film of rust formed almost instantly while drying; just before placing the iron strips in the sample bottle the strips were buifed using a motor driven iron wire wheel. The strips were not permitted to contact the skin after the pickling operation; while buffing they were held with a towel with one end while bufiing the other end, then reversed still using the towel to hold them. It was noticed in previous work that if the strips were touched by the fingers, the oil from the skin adheres thereto and forms corrosion at the point of contact and thereby prevents accurate observation of results.

After storage periods of 2, 5 and 30 days in a 100 F. room, visual observations were taken of the samples to determine approximately the amount of corrosion which had taken place. Amounts of corrosion were classed as negative, trace, slight, medium, and heavy, and were noted on the iron strip within the oil level and also in the water layer where usually it floated free in small particles and a brown haze or sludge developed as the deposit grew. Loose rust tended to break away from the strip in the oil level and settle down into the water level. In a few cases, the rust on the strip in the oil level was fine and adherent to the strip, occurring as a more or less dense layer. In most cases, the oil phase corrosion occurred around small droplets of water which cling to the strip after the original shaking; in such cases the rust was very loose and easily broken free; considerable pitting of the iron strips was noted beneath such bubbles of water and rust. No attempt was made to determine quantitatively the amounts of metal rust due to the two varieties of corrosion. Heavy pitting of the iron strip also tended to concentrate in the water layer. In almost all cases rusting took place on that part of the iron strip which extended into the air in the bottle above the oil level, although in cases of negative to slight rusting, the air rust was reduced. A milky haze was noted in the water layer of several of the samples which had negative or trace corrosion results; it was speculated that perhaps the corrosion inhibitor in these cases was ex tracted from the oil by the water and thus caused the water to become hazy. The following results were obtained:

Example I Cracked Oil with Distilled H2O Rust on Rust Rust on Rust; Rust on Rust Common :51 5 2? 091% by Strip in Loose in Strip in Loose in Strip in Loose in g 011 Level H O Oil Level H20 011 Level H1O After 2 days After 5 days After 30 days 1. Blank slight. slight.... slight medium sligliL... medium. 2. Armeen 12D biguanide negative. negative. negative. negative. negative. negative. 3. Armeen C biguanide o"... on... do. ..do. ..do. Do. 4. N -phenylbiguanide 0 do. ..d0. 0..... .do Do. 5. N -p-toly1-N ,N -di-n-butybbiguado trace- -..do slight... tracemedium.

m'de. 6. Z-amino-fi-dodecylphenylamino-l, trace. negative. trace. trace. .do trace.

4-dihydro-1,3,5-triazine.

a Armeen 12D is a commercially available mixture of alkyl amines, predominately On, which has been purified by fractionation; the water layer under the oil in this case was b Armeen C is a commercially available mixture of alkyl amines, predominately C12.

Example II Virgin Oil with Distilled H10 v Rust on Rust Rust on Rust Rust on Rust az gg by Strip in Loose m Strip in Loose in Strip in Loose m 8 Oil Level 11.0 on Level Hlo Oil Level mo After 2 days After 5 days After 30 days 1. Blank... slight... medium. medium medium. medium. medium. 2. Armeen 12D biguanide negative. negative. negative. negative. trace.... negative 3. Armeen C biguanide do.. .-.do..... trace-... ...do...-. o-.--. trace. 4. N -phenylbiguanide do..--- slight.-.. negative. slight.--. negati negative 5. N -nonylnaphthyl-biguanide-... trace.... negativev sllg trace--.. slight... slight. 6. N -phenyl-N -nbutylbiguanide.. negative. 0..... negative. negative. negative. negative 7. N -phenyl-N -n-hepty1biguanide. ace. 8. N -p-tolyl-N -n-buty1biguanide negative 9. 2 amino-i-phenyl-G-phenyltrace..... slight.

amino 1,4 dillydro 1,3,5 triazine. 10. 2-amino-6-dodecylphenylamino- -..do..-.. negative. do....- trace.-.- negative. Do.

l,4-dihydro-1,3,6-triazine.

1 Water layer clear. b Water layer milky. Water layer clear. 5 Water layer milky.

Example 111 Cracked Oil with Synthetic Sea H10 Rust on Rust Rust on Rust Rust on Rust 00170310 i i 001% by Strip in Loose in Strip in Loose in Strip in Loose in We g Oil Level Hoo Oil Level 11,0 on Level mo After 2 days After 5 days After days 1. Blank heavy..- heavy... heavy--- heavy. 2. Armeen 12D biguanl trace-... traee---. trace-... slight. 3. Armeen C biguanide..-.. sligbt.... ...do..-.. slight.... Do. 4. N -phenyl-N -n-heptylbiguanida --do..-.. slight-.. medium. medium. 5. 2-amino-6-dodecylphenylaminomedium. medium. ...do....- Do.

1,4-d.lhydro-1,3,5-triazine.

Example IV Virgin Oil with Synthetic Sea Water Rust on Rust Rust on Rust Rust on Rust corrosion gg by Strip in Loose in Strip in Loose in Strip in Loose in we 011 Level H on Level rrlo Oil Level Hlo After 2 days After 5 days After 30 days 1. Blank heavy-.- heavy... heavy... heavy. 2. Armeen 12D biguani slight.... slight.... slight... medium. 3. Armeen O biguanide- .do....- ---do slight. 4. N -phenylbiguanide traco--.. trace-... Do. 5. N --pl1enyl--N -n-heptylbiguanide. slight.--. slight.-.. medium.

We claim as our invention:

1. In the handling of organic materials wherein the organic material contacts metal surfaces in the presence of water, the method of inhibiting corrosion of the metal surfaces by said water which comprises dissolving in the organic material from about 0.0001% to about 2% by weight of asubstituted biguanide having a hydrocarbon substituent on at least one of its terminal nitrogen atoms, said organic material and said substituted biguanide being mutually soluble and non-reactive.

2. In the handling of organic materials wherein the organic material contacts metal surfaces in the presence of water, the method of inhibiting corrosion of the metal surfaces by said water which comprises dissolving in the organic material from about 0.0001% to about 2% by weight of a substituted biguanide having a hydrocarbon substituent on each of its terminal nitrogen atoms, said organic material and said substituted biguanide being mutually soluble and non-reactive.

3. In the transportation and storage of hydrocarbon oils where the oil contacts metal surfaces in the presence of water, the method of inhibiting corrosion of the metal surfaces by said water which comprises dissolving in the hydrocarbon oil from about 0.0001% to about 2% by weight of a substituted biguanide having a hydrocarbon substituent on at least one of its terminal nitrogen atoms.

4. In the transportation and storage of hydrocarbon oils where the oil contacts metal surfaces in the presence of water, the method of inhibiting corrosion of the metal surfaces by said water which comprises dissolving in the hydrocarbon oil from about 0.0001% to about 2% by weight of a substituted biguanide having a hydrocarbon substituent on each of its terminal nitrogen atoms.

5. The method of claim 3 further characterized in that said substituted biguanide is an N-alkylbiguanide.

6. The method of claim 3 further characterized in that said substituted biguanide is an N-dodecylbiguanidc.

7. The method of claim 3 further characterized in that said substituted biguanide is an N-dodecylphenylbiguanide.

8. The method of claim 3 further characterized in that said substituted biguanide is an N ,N -di-alkylbiguanide.

9. The method of claim 4 further characterized in that said substituted biguanide has an alkyl substituent on one of its terminal nitrogen atoms and an aryl substituent on the other terminal nitrogen atom.

10. The method of claim 4 further characterized in that said substituted biguanide has an alkyl substituent on one of its terminal nitrogen atoms and an alkylaryl substituent on the other terminal nitrogen atom.

11. The method of claim 4 further characterized in that said substituted biguanide is N -phenyl-N -heptylbiguanide.

References Cited in the file of this patent UNITED STATES PATENTS 

3. IN TH TRANSPORTATION AND STORAGE OF HYDROCARBON OILS WHERE THE OIL CONTACTS METAL SURFACES IN THE PRESENCE OF WATER, THE METHOD OF INHIBITING CORROSION OF THE METAL SURFACES BY SAID WATER WHICH COMPRISES DISSOLVING IN THE HYDROCARBON OIL FROM ABOUT 0.0001% TO ABOUT 2% BY WEIGHT OF A SUBSTITUTED BIGUANIDE HAVING A HYDROCARBON SUBSTITUENT ON AT LEAST ONE OF ITS TERMINAL NITROGEN ATOMS. 